A105 Lectures 18-19 November 3-5, 1997:

Fossil Record of Early Hominids

Earliest Hominid Fossils:

The best-known early hominid fossil species:

  • from sites in Hadar, Afar triangle of Rift in Ethiopia and Laetoli Tanzania found in 1970's and 1980's by teams led by D. Johansen (Hadar) and Mary Leakey (Laetoli)
  • 4-3 million years old
  • small brained, sexually dimorphic biped (e.g. "Lucy")
  • fossilized bipedal footprints at Laetoli
  • mosaic of primitive and derived features on skull and locomotor skeleton (see image of knee) (see image of hand) (see image of pelvis)
  • Take the Lucy Test ! (your instructor is not responsible for the "Lucy Test" site, but thinks it is a worthwhile exercise)

List of important hominid species discussed:

  • Ardipithecus ramidus
    • Ethiopia @ 4.4 mya
    • very primitive (chimp-like) dentition (thin enamel), upright stature determined by foramen magnum
  • Australopithecus anamensis
    • Lake Turkana basin, Kenya @ 3.7-4.2 my
    • primitive dentition, good biped (tibia)
    • read about discovery of Australopithecus anamensis in Kenya!
  • Australopithecus afarensis (e.g. "Lucy" see above)
    • Hadar Ethiopia and Laetoli Tanzania (+ very similar species from a new site in Chad)
    • an evolutionary mosaic of traits: relatively primitive shoulder and arms, long, curved fingers, ape-sized brain; derived bipedal abilities (e.g. pelvis, knee, foot) and dentition
    • sexual dimorphism
    • footprints at Laetoli
  • Australopithecus africanus (e.g. Dart's Taung skull)
    • South African cave sites @ 3.5-2.5 mya
    • body and skull similar overall to A. afarensis, but canine smaller and cheek teeth larger... nice skeletal evidence for bipedalism & body size
  • Australopithecus robustus (also called "Paranthropus robustus")
    • South African cave sites @ 2.5-1.5 mya
    • larger and more robust than africanus... "megadont" with toothwear evidence for chewing coarse vegetable foods (Image of squished skull from Swartkrans)
    • read in textbook about chemical analysis of bones for nutrition
  • Australopithecus aethiopicus
    • Lake Turkana Basin, northern Kenya and Ethiopia @ 2.5 my
    • looks like a very robust A. afarensis (small brain, projecting face, sagital crest and enourmous molars: image of skull)
  • Australopithecus boisei
    • several sites in Ethiopia, Kenya and Tanzania, including Turkana Basin sites and Olduvai Gorge @ 2.0 ~ 1.2 mya
    • megadont, hyper-robust "chewing machines," very sexually dimorphic (image of skull)
  • Homo habilis
    • several sites in Rift Valley, including Ethiopia, Kenya, Tanzania and Malawi; including Turkana Basin sites and Olduvai Gorge @ 2.5 - 1.5 mya
    • gracile skull with small cheek teeth, brain slightly larger than contemporary Australopithecines, but still long arms (images of two specimens: OH24 and KNM-ER1813)
  • Homo rudolfensis
    • ER-1470 specimen, and others, from Turkana Basin sites in Kenya @ 2.0 - 1.8 my
    • larger brain and slightly more robust that H. habilis... originally thought to be male to habilis females, but many now consider different enough to put into own species

Adaptive Radiation of Early Hominids

When? 3.0 - 2.0 my

What happened?

  • cooling/drying climate causes spread of savannas
  • speciation (of antelopes and other species as well as hominids)!
  • Hominid anatomical adaptations = adaptvie radiation
    • diet
    • brain size
  • first evidence of tool use @2.5 mya


WWW links to descriptions and images of early Hominid Fossils and Early Archaeology:

WWW links to climatic change and earth history:

WWW links to fossil primate sites:

Want a WWW change of pace?! Try the following links:

 

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Last updated: 6 Nov, 1997
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